The calibration of voltmeters has previously been accomplished by measuring the outputs obtained upon the application of two known reference voltages and adjusting the transfer function thereof. Typically one of the reference voltages is ground and the other reference voltage is selected so as to produce a near full scale output. The drawback of this method is that separate full scale reference voltages are required for each voltage range, many calibration adjustments are required and `drift` requires periodic calibration to retain full accuracy. Since reference voltages are inherently expensive, especially in the case of high voltage references, it is desirable to calibrate a multirange voltmeter using less than a reference voltage for each range.
It is therefore an object of the present invention to calibrate a voltmeter having multiple ranges without the need for a separate reference voltage for each range.
It is a further object of the present invention to achieve a high degree of accuracy in a voltmeter with a minimum of high precision components and adjustments.
These objects have been accomplished in accordance with the preferred embodiment of the present invention by independently measuring the transfer functions of circuit elements in the voltmeter and logically deriving the transfer functions of the combinations of the circuit elements corresponding to the circuit configurations of the voltmeter for the respective voltage ranges. This transfer function is then logically applied to the output obtained upon the application of an unknown signal so as to produce a calibrated output.